STEAM POWER PLANT Notes | EduRev

: STEAM POWER PLANT Notes | EduRev

 Page 1


    
 
21 
Steam Power Plant 
UNIT 2 STEAM POWER PLANT 
Structure 
2.1 Introduction 
Objectives 
2.2 Basic Consideration in the Analysis of Power Cycles 
2.3 Steam Generator 
2.4 Super Heater 
2.5 Feed Water Heater 
2.6 Furnaces 
2.7 Energy Performance Assessment of Boilers 
2.8 Steam Turbines 
2.9 Condenser 
2.10 Cooling Tower 
2.11 Steam Power Station Control 
2.12 Summary 
2.13 Key Words 
2.14 Answers to SAQs 
 
 
2.1 INTRODUCTION 
Two important area of application of thermodynamics are power generation and 
refrigeration. 
Both power generation and refrigeration are usually accomplished by a system that 
operates on a thermodynamics cycle. 
Thermodynamics cycles can be divided into two generation categories : 
(a) Power Cycles 
(b) Refrigeration Cycles 
The devices or systems used to produce a net power output are often called engines and 
the thermodynamics cycles they operate on are called power cycle. 
The devices or systems use to produce refrigeration are called refrigerator, air 
conditioners or heat pumps and the cycles they operates on are called refrigeration 
cycles. 
Thermodynamic cycles can be categorized as : 
(a) Power cycles or Refrigeration cycles. 
(b) Gas Cycles or Vapor Cycles : In gas cycles, the working fluid remains in 
the gaseous phase throughout the entire cycle, where as in vapor cycles the 
working fluid exists in the vapor phase during one part of the cycle and in 
the liquid phase during another part. 
(c) Closed Cycles or Open Cycles : In closed cycles, the working fluid is 
returned to the initial state at the end of the cycle and is re-circulated. In 
open cycle, the working fluid is renewed at the end of each cycle instead of 
being re-circulated. 
Page 2


    
 
21 
Steam Power Plant 
UNIT 2 STEAM POWER PLANT 
Structure 
2.1 Introduction 
Objectives 
2.2 Basic Consideration in the Analysis of Power Cycles 
2.3 Steam Generator 
2.4 Super Heater 
2.5 Feed Water Heater 
2.6 Furnaces 
2.7 Energy Performance Assessment of Boilers 
2.8 Steam Turbines 
2.9 Condenser 
2.10 Cooling Tower 
2.11 Steam Power Station Control 
2.12 Summary 
2.13 Key Words 
2.14 Answers to SAQs 
 
 
2.1 INTRODUCTION 
Two important area of application of thermodynamics are power generation and 
refrigeration. 
Both power generation and refrigeration are usually accomplished by a system that 
operates on a thermodynamics cycle. 
Thermodynamics cycles can be divided into two generation categories : 
(a) Power Cycles 
(b) Refrigeration Cycles 
The devices or systems used to produce a net power output are often called engines and 
the thermodynamics cycles they operate on are called power cycle. 
The devices or systems use to produce refrigeration are called refrigerator, air 
conditioners or heat pumps and the cycles they operates on are called refrigeration 
cycles. 
Thermodynamic cycles can be categorized as : 
(a) Power cycles or Refrigeration cycles. 
(b) Gas Cycles or Vapor Cycles : In gas cycles, the working fluid remains in 
the gaseous phase throughout the entire cycle, where as in vapor cycles the 
working fluid exists in the vapor phase during one part of the cycle and in 
the liquid phase during another part. 
(c) Closed Cycles or Open Cycles : In closed cycles, the working fluid is 
returned to the initial state at the end of the cycle and is re-circulated. In 
open cycle, the working fluid is renewed at the end of each cycle instead of 
being re-circulated. 
 
22 
 
Power Plant Engineering 
 
Objectives 
After studying this unit, you should be able to 
? know steam generator, steam turbine, and 
? describe cooling towers and condensers. 
2.2 BASIC CONSIDERATION IN THE ANALYSIS OF 
POWER CYCLES 
Actual Cycle 
The cycles encountered in actual devices are difficult to analyze because of the 
presence of complicating effects, such as friction and the absence of sufficient 
time for establishment of the equilibrium conditions during the cycle. 
Ideal Cycle 
When the actual cycle is stripped of all the internal irreversibilities and 
complexities, we end up with a cycle that resembles the actual cycle closely but is 
made up totally of internally reversible processes. Such a cycle is called an Ideal 
cycle. 
Heat Engines 
Heat engines are designed for the purpose of converting other form of 
energy to work and their performance is expressed as thermal efficiency. 
net
th
in
??
W
Q
 
The Idealization and Simplification 
(a) The cycle does not involve any friction. 
(b) All expansion and compression process take place in a quasi-
equilibrium manner. 
(c) The pipe connecting the various component of a system are well 
insulated and heat transfer and pressure drop through them are 
negligible. 
Carnot Cycle 
The Carnot cycle is composed of 4 totally reversible processes : 
(a) Isothermal heat addition at high temperature (T
H
). 
(b) Isentropic expansion from high temperature to low temperature. 
(c) Isothermal heat rejection at low temperature (T
L
). 
(d) Isentropic compression from low temperature to high temperature. 
Thermal efficiency of Carnot cycle = 
th, carnot
1 ? ? ?
L
H
T
T
 
The Carnot Vapor Cycle 
(a) A steady-flow Carnot cycle executed with the saturation dome of a pure 
substance is shown in Figures 2.1(a) and (b). The fluid is heated reversibly 
and isothermally in a boiler (process 1-2), expanded isentropically in a 
turbine (process 2-3), condensed reversibly and isothermally in a condenser 
(process 3-4) and compressed isentropically by a compressor to the initial 
state (process 4-1). 
Page 3


    
 
21 
Steam Power Plant 
UNIT 2 STEAM POWER PLANT 
Structure 
2.1 Introduction 
Objectives 
2.2 Basic Consideration in the Analysis of Power Cycles 
2.3 Steam Generator 
2.4 Super Heater 
2.5 Feed Water Heater 
2.6 Furnaces 
2.7 Energy Performance Assessment of Boilers 
2.8 Steam Turbines 
2.9 Condenser 
2.10 Cooling Tower 
2.11 Steam Power Station Control 
2.12 Summary 
2.13 Key Words 
2.14 Answers to SAQs 
 
 
2.1 INTRODUCTION 
Two important area of application of thermodynamics are power generation and 
refrigeration. 
Both power generation and refrigeration are usually accomplished by a system that 
operates on a thermodynamics cycle. 
Thermodynamics cycles can be divided into two generation categories : 
(a) Power Cycles 
(b) Refrigeration Cycles 
The devices or systems used to produce a net power output are often called engines and 
the thermodynamics cycles they operate on are called power cycle. 
The devices or systems use to produce refrigeration are called refrigerator, air 
conditioners or heat pumps and the cycles they operates on are called refrigeration 
cycles. 
Thermodynamic cycles can be categorized as : 
(a) Power cycles or Refrigeration cycles. 
(b) Gas Cycles or Vapor Cycles : In gas cycles, the working fluid remains in 
the gaseous phase throughout the entire cycle, where as in vapor cycles the 
working fluid exists in the vapor phase during one part of the cycle and in 
the liquid phase during another part. 
(c) Closed Cycles or Open Cycles : In closed cycles, the working fluid is 
returned to the initial state at the end of the cycle and is re-circulated. In 
open cycle, the working fluid is renewed at the end of each cycle instead of 
being re-circulated. 
 
22 
 
Power Plant Engineering 
 
Objectives 
After studying this unit, you should be able to 
? know steam generator, steam turbine, and 
? describe cooling towers and condensers. 
2.2 BASIC CONSIDERATION IN THE ANALYSIS OF 
POWER CYCLES 
Actual Cycle 
The cycles encountered in actual devices are difficult to analyze because of the 
presence of complicating effects, such as friction and the absence of sufficient 
time for establishment of the equilibrium conditions during the cycle. 
Ideal Cycle 
When the actual cycle is stripped of all the internal irreversibilities and 
complexities, we end up with a cycle that resembles the actual cycle closely but is 
made up totally of internally reversible processes. Such a cycle is called an Ideal 
cycle. 
Heat Engines 
Heat engines are designed for the purpose of converting other form of 
energy to work and their performance is expressed as thermal efficiency. 
net
th
in
??
W
Q
 
The Idealization and Simplification 
(a) The cycle does not involve any friction. 
(b) All expansion and compression process take place in a quasi-
equilibrium manner. 
(c) The pipe connecting the various component of a system are well 
insulated and heat transfer and pressure drop through them are 
negligible. 
Carnot Cycle 
The Carnot cycle is composed of 4 totally reversible processes : 
(a) Isothermal heat addition at high temperature (T
H
). 
(b) Isentropic expansion from high temperature to low temperature. 
(c) Isothermal heat rejection at low temperature (T
L
). 
(d) Isentropic compression from low temperature to high temperature. 
Thermal efficiency of Carnot cycle = 
th, carnot
1 ? ? ?
L
H
T
T
 
The Carnot Vapor Cycle 
(a) A steady-flow Carnot cycle executed with the saturation dome of a pure 
substance is shown in Figures 2.1(a) and (b). The fluid is heated reversibly 
and isothermally in a boiler (process 1-2), expanded isentropically in a 
turbine (process 2-3), condensed reversibly and isothermally in a condenser 
(process 3-4) and compressed isentropically by a compressor to the initial 
state (process 4-1). 
    
 
23 
Steam Power Plant 
(b) The Carnot cycle is not a suitable model for vapor power cycle because it 
cannot be approximated in practice.  
 
 
 
 
 
 
 
(a) 
 
 
 
 
 
 
 
 
               (b) 
Figure 2.1 : Carnot Cycle 
Rankine Cycle : The Ideal Cycle for Vapor Power Cycle 
(a) The impracticalities associated with Carnot cycle can be eliminated by 
superheating the steam in the boiler and condensing it completely in the 
condenser. This cycle that results is the Rankine cycle, which is the ideal 
cycle for vapor power plants. The construct of power plant and T-s diagram 
is shown in Figures 2.2(a) and (b). 
 
 
 
 
 
 
 
(a) 
 
 
 
 
 
 
 
(b) 
Figure 2.2 : Rankine Cycle 
1 
4  
3 
2 
T 
s 
4 3 
2 
1 
T 
s 
Boiler  
Turbi
ne 
Condenser  
q out 
W turb,out 
w pump,in 
q in 
Pump  
1 
2 
3 
4 
3 
4’ 1 
2 
T 
s 
w punp,in 
W turb,out 
q in 
q out 
Page 4


    
 
21 
Steam Power Plant 
UNIT 2 STEAM POWER PLANT 
Structure 
2.1 Introduction 
Objectives 
2.2 Basic Consideration in the Analysis of Power Cycles 
2.3 Steam Generator 
2.4 Super Heater 
2.5 Feed Water Heater 
2.6 Furnaces 
2.7 Energy Performance Assessment of Boilers 
2.8 Steam Turbines 
2.9 Condenser 
2.10 Cooling Tower 
2.11 Steam Power Station Control 
2.12 Summary 
2.13 Key Words 
2.14 Answers to SAQs 
 
 
2.1 INTRODUCTION 
Two important area of application of thermodynamics are power generation and 
refrigeration. 
Both power generation and refrigeration are usually accomplished by a system that 
operates on a thermodynamics cycle. 
Thermodynamics cycles can be divided into two generation categories : 
(a) Power Cycles 
(b) Refrigeration Cycles 
The devices or systems used to produce a net power output are often called engines and 
the thermodynamics cycles they operate on are called power cycle. 
The devices or systems use to produce refrigeration are called refrigerator, air 
conditioners or heat pumps and the cycles they operates on are called refrigeration 
cycles. 
Thermodynamic cycles can be categorized as : 
(a) Power cycles or Refrigeration cycles. 
(b) Gas Cycles or Vapor Cycles : In gas cycles, the working fluid remains in 
the gaseous phase throughout the entire cycle, where as in vapor cycles the 
working fluid exists in the vapor phase during one part of the cycle and in 
the liquid phase during another part. 
(c) Closed Cycles or Open Cycles : In closed cycles, the working fluid is 
returned to the initial state at the end of the cycle and is re-circulated. In 
open cycle, the working fluid is renewed at the end of each cycle instead of 
being re-circulated. 
 
22 
 
Power Plant Engineering 
 
Objectives 
After studying this unit, you should be able to 
? know steam generator, steam turbine, and 
? describe cooling towers and condensers. 
2.2 BASIC CONSIDERATION IN THE ANALYSIS OF 
POWER CYCLES 
Actual Cycle 
The cycles encountered in actual devices are difficult to analyze because of the 
presence of complicating effects, such as friction and the absence of sufficient 
time for establishment of the equilibrium conditions during the cycle. 
Ideal Cycle 
When the actual cycle is stripped of all the internal irreversibilities and 
complexities, we end up with a cycle that resembles the actual cycle closely but is 
made up totally of internally reversible processes. Such a cycle is called an Ideal 
cycle. 
Heat Engines 
Heat engines are designed for the purpose of converting other form of 
energy to work and their performance is expressed as thermal efficiency. 
net
th
in
??
W
Q
 
The Idealization and Simplification 
(a) The cycle does not involve any friction. 
(b) All expansion and compression process take place in a quasi-
equilibrium manner. 
(c) The pipe connecting the various component of a system are well 
insulated and heat transfer and pressure drop through them are 
negligible. 
Carnot Cycle 
The Carnot cycle is composed of 4 totally reversible processes : 
(a) Isothermal heat addition at high temperature (T
H
). 
(b) Isentropic expansion from high temperature to low temperature. 
(c) Isothermal heat rejection at low temperature (T
L
). 
(d) Isentropic compression from low temperature to high temperature. 
Thermal efficiency of Carnot cycle = 
th, carnot
1 ? ? ?
L
H
T
T
 
The Carnot Vapor Cycle 
(a) A steady-flow Carnot cycle executed with the saturation dome of a pure 
substance is shown in Figures 2.1(a) and (b). The fluid is heated reversibly 
and isothermally in a boiler (process 1-2), expanded isentropically in a 
turbine (process 2-3), condensed reversibly and isothermally in a condenser 
(process 3-4) and compressed isentropically by a compressor to the initial 
state (process 4-1). 
    
 
23 
Steam Power Plant 
(b) The Carnot cycle is not a suitable model for vapor power cycle because it 
cannot be approximated in practice.  
 
 
 
 
 
 
 
(a) 
 
 
 
 
 
 
 
 
               (b) 
Figure 2.1 : Carnot Cycle 
Rankine Cycle : The Ideal Cycle for Vapor Power Cycle 
(a) The impracticalities associated with Carnot cycle can be eliminated by 
superheating the steam in the boiler and condensing it completely in the 
condenser. This cycle that results is the Rankine cycle, which is the ideal 
cycle for vapor power plants. The construct of power plant and T-s diagram 
is shown in Figures 2.2(a) and (b). 
 
 
 
 
 
 
 
(a) 
 
 
 
 
 
 
 
(b) 
Figure 2.2 : Rankine Cycle 
1 
4  
3 
2 
T 
s 
4 3 
2 
1 
T 
s 
Boiler  
Turbi
ne 
Condenser  
q out 
W turb,out 
w pump,in 
q in 
Pump  
1 
2 
3 
4 
3 
4’ 1 
2 
T 
s 
w punp,in 
W turb,out 
q in 
q out 
 
24 
 
Power Plant Engineering 
 
(b) The ideal Rankine cycle dose not involve any internal irreversibilities  
(c) The Rankine cycle consists of the following four processes : 
1-2 : Isentropic compression in pump (compressors) 
2-3 : Constant pressure heat addition in boiler 
3-4 : Isentropic expansion in turbine 
4-1 : Constant pressure heat rejection in a condenser 
Process 1-2 
Water enters the pump at state 1 as saturated liquid and is compressed 
isentropically to the operating pressure of the boiler. The water temperature 
increases somewhat during this isentropic compression process due to slight 
decrease in the specific volume of the water. The vertical distance between 
state 1 and 2 on the T-s diagram is greatly exaggerated for clarity. 
Process 2-3 
Water enters the boiler as a compressed liquid at state 2 and leaves as a 
superheated vapor at state 3. The boiler is basically a large heat exchanger 
where the heat originating from combustion gases, is transferred to the 
water essentially at constant pressure. The boiler together with the section 
where the steam is superheated (the superheater), is often called the steam 
generator. 
Process 3-4 
The superheated vapor at state 3 enters the turbine, where it expands 
isentropically and produces work by rotating the shaft connected to an 
electric generator. The pressure and the temperature of the steam drops 
during this process to the values at state 4, where steam enters the 
condenser  
Process 4-1 
At this state, the steam is usually a saturated liquid-vapor mixture with a 
high quality. Steam is condensed at constant pressure in the condenser 
which is basically a large heat exchanger, by rejecting heat to a cooling 
medium from a lake, or a river. Steam leaves the condenser as saturated 
liquid and enters the pump, completing the cycle. 
Energy Analysis of the Ideal Rankine Cycle 
All four components associated with the Rankine cycle (the pump, boiler, turbine 
and condenser) are steady-flow devices, and thus all four processes that make up 
the Rankine cycle can be analyzed as steady-flow process. 
The steady flow equation per unit mass of steam reduces to  
  
in out in out
( ) ( ) (kJ/kg) ? ? ? ? ?
ei
q q w w h h 
Pump (q = 0) : 
  
pump, in 2 1 2 1
( ) ( ) ? ? ? ? w h h v P P 
where 
11
1 @ 1 @
and ? ? ?
f p f p
h h v v v 
Boiler (w = 0) : 
  
in 3 2
?? q h h 
Turbine (q = 0) : 
  
turbine, out 3 4
() ?? w h h 
Page 5


    
 
21 
Steam Power Plant 
UNIT 2 STEAM POWER PLANT 
Structure 
2.1 Introduction 
Objectives 
2.2 Basic Consideration in the Analysis of Power Cycles 
2.3 Steam Generator 
2.4 Super Heater 
2.5 Feed Water Heater 
2.6 Furnaces 
2.7 Energy Performance Assessment of Boilers 
2.8 Steam Turbines 
2.9 Condenser 
2.10 Cooling Tower 
2.11 Steam Power Station Control 
2.12 Summary 
2.13 Key Words 
2.14 Answers to SAQs 
 
 
2.1 INTRODUCTION 
Two important area of application of thermodynamics are power generation and 
refrigeration. 
Both power generation and refrigeration are usually accomplished by a system that 
operates on a thermodynamics cycle. 
Thermodynamics cycles can be divided into two generation categories : 
(a) Power Cycles 
(b) Refrigeration Cycles 
The devices or systems used to produce a net power output are often called engines and 
the thermodynamics cycles they operate on are called power cycle. 
The devices or systems use to produce refrigeration are called refrigerator, air 
conditioners or heat pumps and the cycles they operates on are called refrigeration 
cycles. 
Thermodynamic cycles can be categorized as : 
(a) Power cycles or Refrigeration cycles. 
(b) Gas Cycles or Vapor Cycles : In gas cycles, the working fluid remains in 
the gaseous phase throughout the entire cycle, where as in vapor cycles the 
working fluid exists in the vapor phase during one part of the cycle and in 
the liquid phase during another part. 
(c) Closed Cycles or Open Cycles : In closed cycles, the working fluid is 
returned to the initial state at the end of the cycle and is re-circulated. In 
open cycle, the working fluid is renewed at the end of each cycle instead of 
being re-circulated. 
 
22 
 
Power Plant Engineering 
 
Objectives 
After studying this unit, you should be able to 
? know steam generator, steam turbine, and 
? describe cooling towers and condensers. 
2.2 BASIC CONSIDERATION IN THE ANALYSIS OF 
POWER CYCLES 
Actual Cycle 
The cycles encountered in actual devices are difficult to analyze because of the 
presence of complicating effects, such as friction and the absence of sufficient 
time for establishment of the equilibrium conditions during the cycle. 
Ideal Cycle 
When the actual cycle is stripped of all the internal irreversibilities and 
complexities, we end up with a cycle that resembles the actual cycle closely but is 
made up totally of internally reversible processes. Such a cycle is called an Ideal 
cycle. 
Heat Engines 
Heat engines are designed for the purpose of converting other form of 
energy to work and their performance is expressed as thermal efficiency. 
net
th
in
??
W
Q
 
The Idealization and Simplification 
(a) The cycle does not involve any friction. 
(b) All expansion and compression process take place in a quasi-
equilibrium manner. 
(c) The pipe connecting the various component of a system are well 
insulated and heat transfer and pressure drop through them are 
negligible. 
Carnot Cycle 
The Carnot cycle is composed of 4 totally reversible processes : 
(a) Isothermal heat addition at high temperature (T
H
). 
(b) Isentropic expansion from high temperature to low temperature. 
(c) Isothermal heat rejection at low temperature (T
L
). 
(d) Isentropic compression from low temperature to high temperature. 
Thermal efficiency of Carnot cycle = 
th, carnot
1 ? ? ?
L
H
T
T
 
The Carnot Vapor Cycle 
(a) A steady-flow Carnot cycle executed with the saturation dome of a pure 
substance is shown in Figures 2.1(a) and (b). The fluid is heated reversibly 
and isothermally in a boiler (process 1-2), expanded isentropically in a 
turbine (process 2-3), condensed reversibly and isothermally in a condenser 
(process 3-4) and compressed isentropically by a compressor to the initial 
state (process 4-1). 
    
 
23 
Steam Power Plant 
(b) The Carnot cycle is not a suitable model for vapor power cycle because it 
cannot be approximated in practice.  
 
 
 
 
 
 
 
(a) 
 
 
 
 
 
 
 
 
               (b) 
Figure 2.1 : Carnot Cycle 
Rankine Cycle : The Ideal Cycle for Vapor Power Cycle 
(a) The impracticalities associated with Carnot cycle can be eliminated by 
superheating the steam in the boiler and condensing it completely in the 
condenser. This cycle that results is the Rankine cycle, which is the ideal 
cycle for vapor power plants. The construct of power plant and T-s diagram 
is shown in Figures 2.2(a) and (b). 
 
 
 
 
 
 
 
(a) 
 
 
 
 
 
 
 
(b) 
Figure 2.2 : Rankine Cycle 
1 
4  
3 
2 
T 
s 
4 3 
2 
1 
T 
s 
Boiler  
Turbi
ne 
Condenser  
q out 
W turb,out 
w pump,in 
q in 
Pump  
1 
2 
3 
4 
3 
4’ 1 
2 
T 
s 
w punp,in 
W turb,out 
q in 
q out 
 
24 
 
Power Plant Engineering 
 
(b) The ideal Rankine cycle dose not involve any internal irreversibilities  
(c) The Rankine cycle consists of the following four processes : 
1-2 : Isentropic compression in pump (compressors) 
2-3 : Constant pressure heat addition in boiler 
3-4 : Isentropic expansion in turbine 
4-1 : Constant pressure heat rejection in a condenser 
Process 1-2 
Water enters the pump at state 1 as saturated liquid and is compressed 
isentropically to the operating pressure of the boiler. The water temperature 
increases somewhat during this isentropic compression process due to slight 
decrease in the specific volume of the water. The vertical distance between 
state 1 and 2 on the T-s diagram is greatly exaggerated for clarity. 
Process 2-3 
Water enters the boiler as a compressed liquid at state 2 and leaves as a 
superheated vapor at state 3. The boiler is basically a large heat exchanger 
where the heat originating from combustion gases, is transferred to the 
water essentially at constant pressure. The boiler together with the section 
where the steam is superheated (the superheater), is often called the steam 
generator. 
Process 3-4 
The superheated vapor at state 3 enters the turbine, where it expands 
isentropically and produces work by rotating the shaft connected to an 
electric generator. The pressure and the temperature of the steam drops 
during this process to the values at state 4, where steam enters the 
condenser  
Process 4-1 
At this state, the steam is usually a saturated liquid-vapor mixture with a 
high quality. Steam is condensed at constant pressure in the condenser 
which is basically a large heat exchanger, by rejecting heat to a cooling 
medium from a lake, or a river. Steam leaves the condenser as saturated 
liquid and enters the pump, completing the cycle. 
Energy Analysis of the Ideal Rankine Cycle 
All four components associated with the Rankine cycle (the pump, boiler, turbine 
and condenser) are steady-flow devices, and thus all four processes that make up 
the Rankine cycle can be analyzed as steady-flow process. 
The steady flow equation per unit mass of steam reduces to  
  
in out in out
( ) ( ) (kJ/kg) ? ? ? ? ?
ei
q q w w h h 
Pump (q = 0) : 
  
pump, in 2 1 2 1
( ) ( ) ? ? ? ? w h h v P P 
where 
11
1 @ 1 @
and ? ? ?
f p f p
h h v v v 
Boiler (w = 0) : 
  
in 3 2
?? q h h 
Turbine (q = 0) : 
  
turbine, out 3 4
() ?? w h h 
    
 
25 
Steam Power Plant 
Condenser (w = 0) 
  
out 4 1
?? q h h 
The thermal efficiency of the Rankine cycle is determine from 
  
net out
th
in in
1 ? ? ? ?
wq
qq
 
where  
net in out turbine, out pump, in
? ? ? ? w q q w w 
Deviation of Actual Vapor Power Cycle from Idealized Ones 
The actual vapor power cycle differs from the ideal Rankine cycle, as a result of 
irreversibilites in various components. Fluid friction and heat loss to the 
surroundings are the two common sources of irreversibilites. 
Fluid friction causes pressure drop in the boiler, the condenser and the piping 
between various components. Also the pressure at the turbine inlet is somewhat 
lower than that at the boiler exit due to the pressure drop in the connecting pipes. 
To compensate for these pressure drops, the water must be pumped to a 
sufficiently higher pressure than the ideal cycle. This requires a large pump and 
larger work input to the pump, are shown in Figures 2.3(a) and (b). 
 
 
 
 
 
 
 
 
 
(a) 
 
 
 
 
 
 
 
 
 
 
 
(b) 
Figure 2.3 : Vapour Power Cycle 
The other major source of irreversibility is the heat loss from the steam to the 
surrounding as the steam flows through various components. 
Particular importance is the irreversibilites occurring within the pump and the 
turbine. A pump requires a greater work input, and a turbine produces a smaller 
T 
s 
IDEAL CYCLE 
Pressure drop 
in the pump   
Pressure drop in 
the boiler  
Irreversibility in 
the turbine   
Pressure drop in 
the condenser    
4 
3 
2 
1 
ACTUAL CYCLE  
2a 
2s 
1 
4s 4a 
s 
T 
3 
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